电子与通信工程硕士专业英语part-6.pptx

2020 3 20 1 Lesson3电信Telecommunications UNIT8PassageB Intensivereading 1 2 2020 3 20 2 Lesson3电信Telecommunications 技术背景Background ThefourphasesoftheevolutionofcommunicationsnetworksareshowninTable8 1 2020 3 20 3 Lesson3电信Telecommunications 技术背景Background 2020 3 20 4 Lesson3电信Telecommunications 内容大纲Outline HardwareandSoftware Hardware Software Applications Host Terminal File Transfer Computer Network 2020 3 20 5 Lesson3电信Telecommunications 内容大纲Outline TelecommunicationServices Network InformationRetrieval ElectronicMail BulletinBoard OngoingDevelopments 2020 3 20 6 preface Lesson3电信Telecommunications Telecommunicationsarethetransmissionofwords sounds images ordataintheformofelectronicorelectromagneticsignalsorimpulses Transmissionmediaincludethetelephone usingwireoropticalcable radio television microwave andsatellite Datacommunication thefastestgrowingfieldoftelecommunication istheprocessoftransmittingdataindigitalformbywireorradio 精读详解Intensivereading 2020 3 20 7 preface Lesson3电信Telecommunications Digitaldatacanbegenerateddirectlyina1 0binarycodebyacomputerorcanbeproducedfromavoiceorvisualsignalbyaprocesscalledencoding Adatacommunicationsnetworkiscreatedbyinterconnectingalargenumberofinformationsourcessothatdatacanflowfreelyamongthem Thedatamayconsistofaspecificitemofinformation agroupofsuchitems orcomputerinstructions Exampleincludeanewsitem abanktransaction amailingaddress aletter abook amailinglist abankstatement oracomputerprogram 精读详解Intensivereading 2020 3 20 8 preface Lesson3电信Telecommunications Thedevicesusedcanbecomputers terminals devicesthattransmitandreceiveinformation andperipheralequipmentsuchasprinters Thetransmissionlineusedcanbeanormaloraspeciallypurchasedtelephonelinecalledaleased orprivateline Itcanalsotaketheformofamicrowaveoracommunications satellitelinkage orsomecombinationofthesevarioussystems 精读详解Intensivereading 2020 3 20 9 HardwareandSoftware Lesson3电信Telecommunications Eachtelecommunicationsdeviceuseshardware whichconnectsadevicetothetransmissionline andsoftware whichmakesitpossibleforadevicetotransmitinformationthroughtheline HardwareHardwareusuallyconsistsofatransmitterandacableinterface orifthetelephoneisusedasatransmissionline amodulator demodulator ormodem 精读详解Intensivereading 2020 3 20 10 HardwareandSoftware Lesson3电信Telecommunications Acableinterface asthenameindicates connectsadevicetoacable Itconvertsthetransmittedsignalsfromtheformrequiredbythedevicetotheformrequiredbythecable 精读详解Intensivereading 2020 3 20 11 HardwareandSoftware Lesson3电信Telecommunications SoftwareAmongthedifferentkindsofsoftwarearefile transfer hostandnetworkprograms File transfersoftwareisusedtotransmitadatafilefromonedevicetoanother Hostsoftwareidentifiesahostcomputerassuchandcontrolstheflowofdataamongdevicesconnectedtoit Networksoftwareallowsdevicesinacomputernetworktotransmitinformationtooneanother 精读详解Intensivereading 2020 3 20 12 Applications Lesson3电信Telecommunications Host TerminalInthesetypesofcommunications onecomputer thehostcomputer isconnectedtooneormoreterminals Eachterminaltransmitsdatatoorreceivesdatafromthehostcomputer Forexample manyairlineshaveterminalsthatarelocatedatthedesksofticketagentsandconnectedtoacentral hostcomputer Theseterminalsobtainflightinformationfromthehostcomputer whichmaybelocatedhundredsofkilometersawayfromtheagent ssite 精读详解Intensivereading 2020 3 20 13 Applications Lesson3电信Telecommunications File Transfer Anoutgrowthoffiletransferiselectronicmail Forexample anemployeemightwriteadocumentsuchasaletter memorandum orreportonacomputerandthensendthedocumenttoanotheremployee scomputer 精读详解Intensivereading 2020 3 20 14 Applications Lesson3电信Telecommunications Computer Network Thethreekindsofcomputernetworksarelocalareanetworks LAN privatebranchexchange PBX networks andwide areanetworks WAN LANsinterconnectdeviceswithagroupofcables thedevicescommunicateatahighspeedandmustbeincloseproximity 精读详解Intensivereading 2020 3 20 15 Applications Lesson3电信Telecommunications APBXnetworkinterconnectsdeviceswithatelephoneswitchingsystem inthiskindofnetwork thedevicesmustagainbeincloseproximity Inwide areanetworks ontheotherhand thedevicescanbeatgreatdistancesfromoneanother andsuchnetworksusuallyinter connectdevicesbymeansoftelephone 精读详解Intensivereading 2020 3 20 16 TelecommunicationServices Lesson3电信Telecommunications NetworkApublicnetworkserviceleasestimeonaWAN therebyprovidingterminalsinothercitieswithaccesstoahostcomputer ExamplesofsuchservicesincludeTelenet Tymnet Uninet andDatapac Theseservicessellthecomputingpowerofthehostcomputertouserswhocannotordonotwishtoinvestinthepurchaseofsuchequipment 精读详解Intensivereading 2020 3 20 17 TelecommunicationServices Lesson3电信Telecommunications InformationRetrievalAninformation retrievalservicesleasestimeonahostcomputertocustomerswhoseterminalsareusedtoretrievedatafromthehost AnexampleofthisisCompuServe whosehostcomputerisaccessedbymeansofthepublictelephonesystem Thisandothersuchservicesprovidegeneral purposeinformationonnews weather sports finances andshopping 精读详解Intensivereading 2020 3 20 18 TelecommunicationServices Lesson3电信Telecommunications ElectronicMail BulletinBoardBymeansofabulletinboard terminalsareabletofacilitateexchangesandothertransactions Manybulletinboardsdonotchargeafeefortheirservices Usersoftheseservicessimplyexchangeinformationonhobbies buyandsellgoodsandservices andexchangecomputerprograms 精读详解Intensivereading 2020 3 20 19 OngoingDevelopments Lesson3电信Telecommunications Certaintelecommunicationmethodshavebecomestandardinthetelecommunicationsindustryasawhole becauseiftwodevicesusedifferentstandardstheyareunabletocommunicateproperly Standardsaredevelopedintwoways 1 themethodissowidelyusedthatitcomestodominate 2 themethodispublishedbyastandard settingorganization 精读详解Intensivereading 2020 3 20 20 OngoingDevelopments Lesson3电信Telecommunications ThemostimportantorganizationinthisrespectistheInternationalTelecommunicationUnion aspecializedagencyoftheUnitedNationsandoneofitsoperationalentities theInternationalTelegraphandTelephoneConsultativeCommittee CCITT OtherorganizationsintheareaofstandardsaretheAmericanNationalStandardsInstitute ANSI theInstituteofElectricalEngineers IEE andtheElectronicIndustriesAssociation 精读详解Intensiv